In the end, they sat together in the cavernous downstairs room of her mother's Cleveland Park home -- Zoe FitzGerald Carter, her husband Joe Guth, and her sister Sarah Barron -- and they waited.

It was agonizing and terrible, but final. This wait would be the last after years of planning, crying, guilt, resentment, replanning, recommitting. This night meant the end of debating what was legal vs. what was moral, and whether either was as important as what was kind.

They gathered in the big room that Zoe's father had used for music rehearsals, and then they moved upstairs, near the bed where Mary FitzGerald Carter lay, an overdose of morphine coursing through her frail, starved body. At some point Zoe gave into exhaustion, fell asleep and dreamed that she was talking to her mother. Morning arrived. Then Sarah shook Zoe awake to tell her.

Their mother hadn't died, Sarah said.

The journey that led to that big room began a year earlier, in 2000, when Mary FitzGerald Carter resolved to kill herself and announced that she wanted her children present.

Or maybe it began 20 years before that, when Mary, then a vibrant 50-something, noticed a tremor in her hand. A diagnosis came, Parkinson's disease, followed by decades of slow degeneration, a loss of easy movement, a rigidity to her handsome face.

Or maybe it began when she had three daughters. Sons might have missed their mother just as deeply and been just as involved in her care. In the drawn-out death of a parent, relationships can be broken or mended; wounds thought healed are discovered to be merely scabbed over. But relationships between mothers and daughters and sisters are already notoriously fraught -- love tinged with guilt and expectation, with the desire to be a "good daughter."

"What does it mean, to be a good daughter?" Zoe asks. "Should I have helped her to die or should I have stopped her?"

Her new memoir, "Imperfect Endings," revisits the last year of her mother's life -- the scene in the big room and all the events leading up to it -- in all of its horror, beauty and mundanity.

What kind of good daughter would help end her mother's life, and what kind of good mother would ask her to? Exactly how far does "Honor thy mother" extend?

In some ways, "Imperfect Endings" is not only a memoir of a family but of Washington in a certain place and time. The Carters were typical of the Cleveland Park liberal intelligentsia of the 1960s and '70s. They threw parties and went to inaugural balls. They practiced meditation, joined a Quaker meeting house, loved music and art, singing and craft projects. Mary studied for two master's degrees, in psychology and literature. She wore a fur coat and black tights from Europe, which gave her an aura of "glamour," according to Jeanne Shorey, a former neighbor.

"She had a regal quality about her, but she was also very persevering," Shorey remembers, recalling the time that, for a writing project, Mary hid in the bathroom of a Boston hotel so she could perfectly capture the workers' Irish accents.